Ph.D. student, Oxford Brookes University

Since October 2004, I have been conducting research in one of the world’s most diverse, yet endangered, eco-regions – the southwestern Wet Zone of Sri Lanka – carrying out the first long-term study of the social organization and habitat use of an endangered and newly identified nocturnal primate species, the red slender loris (Loris tardigradus tardigradus). The study is being carried out in a highly disturbed and fragmented monsoon forest containing a wide range of predators. Radio-telemetric data and focal observations on ranging, use of space, dispersal movements, social behaviour and sleeping group composition are collected in order to illuminate the social organization of Loris tardigradus tardigradus. These data will be examined in the context of hypotheses regarding the effects of habitat fragmentation, and the impact of predation and resource distribution on its behavioural ecology

PROJECT REPORT: October 2006

Behavioural data were collected on a population of Loris tardigradus tardigradus in a fragmented and disturbed lowland rainforest in the Matara District, Masmullakele Proposed Forest Reserve (Masmulla PFR). In addition, seventeen adult slender lorises, nine males and eight females, were followed using radio-telemetry. Data on home range size were also collected on three non-collared juveniles. Acoustic data were collected and a total of 180 calls were digitized for analysis. Vegetation surveys were conducted in order to assess the floristic composition and forest structure of Masmulla PFR. Preliminary results of the study are detailed below.

Although Masmulla PFR has been heavily exploited, it is floristically interesting as it occurs at the intersection of three floristic zones, where dry zone, intermediate zone and wet zone species occur together. Of the total number of species recorded at Masmulla PFR, 35 % were endemic.

Slender lorises at Masmulla PFR preferred to use small substrates over medium and larger ones. Substrate type included lianas, vines, branches, trunks and ground. Substrate orientation appeared to be related to the activity. For example, traveling more often occurred on horizontal and oblique substrates, whereas a lot of the foraging activity would involve moving up and down vertical substrates. Some animals would come down to the ground a lot more often than others and it was always associated with foraging. Height preference varied according to the individual, with some of the radio-collared animals showing a preference for heights > 5m, and others spending the majority of the night < 5 m. Some animals showed a preference for foraging on the ground whereas others would rarely come down below 1 m.

No slender lorises were ever seen using paddy fields or plantations (cinnamon, banana). However it was common to see slender lorises using 'abandoned' pine forests where secondary forest had regenerated. In these pine forests, dense scrub-like vegetation appeared to be favored by some animals for foraging, as well as resting during the night. Some slender lorises also showed preference for edge habitat over inland forest habitat, in which case they would often come close to home gardens. However, none of these animals were ever seen venturing too far away from the forest edge.

Radio-telemetric data indicates that home range size of L. t. tardigradus ranges between 1.5 and 12 ha and varies more between females than between males. Variation between female home range sizes was bigger than variation between male home range sizes. Home range overlap appears to be greater intersexually than intrasexually, with overlap between females being smaller than between males. Social contacts amongst the slender lorises of Masmulla PFR were frequent. They formed sleeping groups of up to four animals, engaged in intense grooming at dusk and at dawn, often met throughout the night during which time chasing, playing or fighting occurred, and were regularly communicating amongst each other throughout the night with the use of loud calls. However, they did spend the majority of the night traveling and foraging within their home range alone, or at least 50 m away from another individual, during which time loud calls might be uttered. Without analysis of radio-telemetry data it is difficult to say with confidence, which type of social organization slender lorises at Masmull PFR have. However, based on preliminary analysis, evidence shows that they may have a 'dispersed multimale-multifemale' type social organisation. Preliminary analysis of acoustic data reveals a much wider and more complex vocal repertoire than previously thought. Finally, work was conducted to raise slender loris awareness through the development of a small slender loris information booklet.